The invention relates to a combined cooling plant and heat pump, especially for the heating and cooling of the passenger compartments of motor vehicles.
Cooling plants and heat pumps are used to cool or heat rooms of buildings. The varying weather conditions caused by the sequence of seasons frequently require a heating system in winter and transitional periods, and a cooling system in summer.
The state-of-the-art includes, apart from the monofunctional use of cooling plants and heat pumps, the combination of these devices, for example, to alternatively heat or cool rooms such-as habitable or-office rooms and storerooms as well, or to cool and heat the passenger compartments of motor vehicles.
This application clearly indicates the potential of the combination and mutual completion of cooling plants and heat pumps.
Future vehicle engines are expected to yield sufficient amounts of heat to heat the passenger compartments, but not at the required temperature level. Therefore, in some diesel-driven vehicles, supplementary heating systems with heater plugs, resistance heating or fuel-fired burners, have been provided.
This is due to the fact that modern combustion engines or electric motors tend to produce smaller amounts of waste heat at lower temperatures and hence, can no longer make available the amounts of heat at the temperature level required to heat the passenger compartments. Particularly in winter, the cold-start phase is a problem.
More and more motor vehicles are equipped with cooling plants to air condition the passenger compartments in summer.
Another possibility to enhance the heating situation in motor vehicles is to utilize the provided cooling plant as a heat pump in summer.
It is know from the state-of-the-art to combine cooling plants and heat pumps for the use in motor vehicles.
Use of various blocking devices and supplementary connection lines enables to change the heat input and output functions of the heat exchangers in such a system. The heat exchanger for cooling the passenger compartment is the evaporator of the cooling system and becomes the condenser/gas cooler of the heat pump in the heating mode.
The technical problem is essentially the economic acceptability of the approaches that can be technically realized.
In providing a cooling system for a passenger compartment it is, first, necessary to have a minimum of additional components, which are needed for heating operation and second, to design these components as useful and multifunctional as possible.
According to the concept of EP 0 945 290 A2, a cooling system of a combustion engine drive vehicle is modified in such a way that by means of an additional waste gas heat exchanger and two additional multiway blocking devices piped according to the invention, both the cooling system and heating operational modes are possible dependent on the temperature requirements inside the passenger compartment.
It is a specific disadvantage of this known state-of-the-art that the solution, according to EP 0 945 290 A2, that a combined cooling heating operation requires expensive circuitry and increases the cost of the device by making it necessary to use several multiway valves, or mode selectors, respectively, and a sophisticated expansion valve that can be passed in different directions of flow, or even two expansion valves with the necessary connection lines and blocking devices.
The concept according to the invention is that the combined cooling and heat pump plant has a decompression device that fulfills the functions of a decompression device and of a mode switch, or of a 3/2-directional valve for the cooling plant or heat pump modes, and the function of a safety device as well.
Therefore the decompression device according to the invention has three connections for coolant conduits and is entered by the high pressure coolant, depending on cooling or heat pump operational mode, at one side in each case. Depending on the entering direction of the coolant, different flow paths are provided, whereby these different flow paths are defined by a mechanically acting channel element which, actuated by the pressure of the flowing coolant automatically, takes two positions in the decompression device dependent on the entering direction of the coolant.
In the cooling mode position of the channel element, two connections of the coolant conduits are low pressure, namely, the glycol heat exchanger and the evaporator. In this operational mode, all three connections are connected to each other via the channel element.
In the heat pump mode position of the channel element, the connection leading to the glycol heat exchanger is low pressure and the connection leading to the outside heat exchanger is blocked.
The advantage of the invention is that dependent on the direction of flow, and thus on the operational mode of the device, the decompression function and the blocking function, or the pressure relief function are realized by only one component, namely the decompression device.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.